Synthesis, Characterization and Preliminary Antimicrobial Studies of Some Schiff Base Ligands and Their Co(Ii), Mn(Vii), Mo(Vii) Complexes

Synthesis, Characterization, and Preliminary Antimicrobial Studies of Some Schiff Base Ligands and Their Co(Ii), Mn(Vii), Mo(Vii) Complexes

Chapter One

AIM AND OBJECTIVES OF THE RESEARCH

The relationship between metal ions and biological activity of certain systems is obvious and a subject of great interest. It has been demonstrated that biologically inactive compounds become active and less biologically active compounds become more active upon coordination with the metal ions (Okeke, 2018). The apparent role played by metal ions in the induction or enhancement of biological activity of the organic compounds is therefore definite, but how, is still not well understood.

In order to get an insight into this role, the behaviour of Schiff bases has gained a great deal of attraction. The imine linkage (– N = CH-) is a significant feature that makes Schiff base ligands interesting for biological activities as well as coordination with the metal ions. The interaction between these metal ions and such biologically active ligands should serve as a route in designing new metal-based drugs for bacteria, fungi, microbes, HIV, etc strains that have become resistant to the use of conventional drugs.

This study therefore is aimed at;

Synthesizing two new Schiff base ligands by capping the amine group in 1,4-phenylenediamine with 4-dimethylaminobenzadehyde and 2-hydroxylbenzadehyde.
Preparation of their metal complexes by refluxing in absolute ethanol using Co(II), Mo(VI), and Mn(VI) metal salts.
Characterizing the formed ligands and their different metal complexes on the basis of their;

i) Melting point
ii) Electronic Spectra
Infrared spectra
Microbial analysis

CHAPTER TWO

LITERATURE REVIEW

Sibous et al., (2013) synthesized, characterised and studied the electrochemical behaviour of Co(II), Ni(II) and Cd(II) complexes with N₂O₂ donor ligands derived from 4,4’-diaminobiphenyl and 2-hydroxybenzaldehyde or 2,4-dihydroxybenzaldehyde. The coordination of the metal ions is through nitrogen and oxygen atoms. The cobalt(II) and cadmium(II) compounds presented a distorted tetrahedral geometry while nickel(II) complexes exhibited a typical square planar structure.

Suresh et al.,(2010) synthesized a new series of transition metal complexes of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) from the Schiff base ligand derived from 4-aminoantipyrine, furfural and o-phenylenediamine. The structural features were derived from their elemental analyses, infrared, UV-visible spectroscopy, NMR spectroscopy, thermal gravimetric analyses, ESR spectral analyses and conductivity measurements. The data of the complexes suggested square planar geometry for the metals with primary valence of two. Antimicrobial screening tests were performed against bacteria. The comparative study of the MIC values of the Schiff base and its metal complexes indicated that the metal complexes exhibited greater antibacterial activity than the free ligand.

Abdunnaser et al.,(2013) studied the uptake properties of the Schiff bases derived from salicylaldehyde and 4-dimethylaminobenzaldehyde, 1,8-naphthalenediamine, or 2-aminobenzoyl alcohol. These Schiff bases were synthesised, characterized and subjected to complexation reactions. A series of transition and heavy metals such as Zinc (II), Cobalt (II), Lead (II), cadmium (II) formed stable complexes with the obtained Schiff bases. The Schiff bases and their complexes, for comparison, have been studied by simple conventional techniques. Various analytical parameters such as: Melting points, pH values, solubility in different solvents, infrared spectroscopy, electrical conductivity and atomic absorption spectroscopy were used. Moreover, the only Schiff base obtained from salicylaldehyde and 1,8-naphthalenediamine was considered and was subjected and evaluated for its influence on the metal ions uptake behaviour. The condition and coordination of the sites and metal ions properties agreed with the data obtained from the tools used in the analysis. To this end, a number of compounds were formulated, and such Schiff bases were found to possess the uptake properties. Attempts were made this to find out the best uptake properties.

CHAPTER Three

MATERIALS AND METHOD

MATERIALS/APPARATUS

Mechanical stirrer
Glass wares
Pot
Boiling ring
Heating mantle
Aspirator bucket
Reflux condenser
Retort stand and clamp
Fridge
Nose mask
Sample analysis bottles
Fume cupboard
Water hose
Thermometer (0ᵒ-360ᵒc)
Filter paper
Hand gloves
Weighing balance

REAGENTS

The reagents used for the research include the following;

1,4-phenylenediamine
4- Dimethylaminobenzadehyde
Ammonium molybdate
Potassium tetraoxomanganate(IV)
Cobalt(II) chloridedihydrate
2- hydroxybenzadehyde
Silica gel
Acetic acid
Ethanol
Methanol
Benzene
Butanol
Propan -2-one
Dimethyl sulfoxide
Nutrient agar
Distilled water

The Microorganisms used are Candida albicans, Escherichia coli, Salmonella typhi, Enterococcus feacalis and Staphylococcus aureus.

CHAPTER FOUR

RESULTS AND DISCUSSION

For clarity reasons these abbreviations were used

M → N,N^/Bis(2-hydroxylbenzylidene) -1,4-phenylenediimine

N→ N,N^/Bis(4-dimethylaminobenzylidene)-1,4-phenylenediimine

CoM→ Co(II) complex of N,N^/Bis (2-hydroxylbenzylidene) -1,4-phenylenediimine

MnM →Mn(VII) complex of N,N^/Bis (2-hydroxylbenzylidene) -1,4-phenylenediimine

Mo₂M → Mo(VII) complex of N,N^/Bis (2-hydroxylbenzylidene) -1,4-phenylenediimine

CoN → Co(II) complex of N,N^/Bis(4-dimethylaminobenzylidene)-1,4-phenylenediimine

MnN→ Mn(VII) complex of N,N^/Bis(4-dimethylaminobenzylidene)-1,4-phenylenediimine

Mo₂N→Mo(VII) complex of N,N^/Bis(4-dimethylaminobenzylidene)-1,4-phenylenediimine

CHAPTER FIVE

CONCLUSION AND RECOMMENDATION

The chemistry of Schiff bases is a field that is being noticed. Schiff base ligands are considered privileged ligands because they are easily prepared by a simple condensation of an aldehyde derivatives and primary amines. The synthesis and characterization of the ligands N,N^/Bis (2-hydroxylbenzylidene) -1,4-phenylenediimine,(M) and N,N^/Bis(4-dimethylaminobenzylidene)-1,4-phenylenediimine (N) with its Co(II), Mn(VII) and Mo(VII) complexes all obtained as powders were possible with respect to their various methods of preparations. Generally, these compounds have yellow and dark brown colours with high melting point and high molar absorptivity. The result of the electron spectra and infrared spectra shows that there was coordination between the ligands and metal complexes. The antimicrobial result showed that there were higher activities on the gram negative organism than on the gram positive organism.

It was observed from this preliminary study that these ligands are virgin and novel. Thus, they can serve as starting materials for some organic, coordination, kinetics, polymer and other branches of chemistry researches. These compounds and their metal complexes had a variety of applications including clinical, analytical, agrochemical industry they also play important roles in catalysis and corrosion inhibitor. Due to the high melting points of these ligands and complexes, they can be employed in high technology industries were high melting point are required. More conclusions concerning these structures in this work could be made with further studies involving elemental analysis, x-rays, electron spin resonance, crystallography, magnetic and conductivity measurements. This would be a good research starting point which would require variation of substituents on the same structural nucleus and elucidation of the mechanism of the variation in the microbial property of the ligands and their complexes.

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